The Shaman illusion spell Form of the Great Bear is supposed to use a black-haired version of the brown bear model, NOT the kodiak model. The brown bear model has an open mouth and a longer lower jaw.
I have a classic era screenshot which shows a Troll shaman in bear form:
Troll (no illusion): http://i.imgur.com/KBxUV4W.png
Same Troll (bear illusion): http://i.imgur.com/8A9toVN.png
Here's what the current Troll illusion bear looks like, notice that the mouth is closed (this is the kodiak model):
http://i.imgur.com/mQ13atr.jpg